More smoke and smoke colour
Your file has a fluid object where Smoke Color is set to black, and in your domain material, the Color in the Principled Volume node is also set to black. If you want colored smoke, you have to set colors to the volume at some point or another.
Sorry for a very long answer now but I want to give you examples on how to use color on the smoke. It works like this - I'm using two Flow Objects in a single domain with only one domain material:

In the settings of the Flow Object you can specify a Smoke Color. This is first of all shown in the Solid View so you can distinguish them in the 3D Viewport.



In Rendered View however, if your domain material is set to the default grey color without any Color Attribute set, it shows the default grey.



If you enter the Color Attribute &quot;color&quot;, the smoke gets colored by the Flow Object settings, but they are darker than the original colors because they are combined with the grey color set in the Principled Volume node.



You can even give them a different tint by keeping the attribute and changing the node's color setting. I don't understand exactly how the colors are mixed, I guess it has something to do with volume absorption.



A different way to color the smoke is to use the Volume Info node. If you plug it into the Color socket of the Principled Volume shader without using the Color Attribute, it colors the smoke according to the settings of the Flow Objects.



This is just the same as if you were using the Color Attribute and combining it with full white in the node's Color setting.



Using both the Volume Info node and the Color Atrribute will combine each color with itself instead of a single tint for both, meaning it will make the colors more intense (and maybe a little darker, too).